🔐 Base64 Encoder

Convert any text into Base64. Encoding happens entirely in your browser — nothing you type is ever sent to a server. UTF-8 is handled correctly, so emoji and non-Latin scripts encode exactly as they should.

Text to encode

Encoded live as you type.

Options

URL-safe alphabet (-_ instead of +/, no padding) Wrap at 76 characters (MIME)

From characters to bytes to Base64

Your text is first turned into UTF-8 bytes, then every three bytes become four characters of six bits each, padded with = to a multiple of four. That is why the three counters above rarely agree:

"cafe" with an accented e   4 characters   5 bytes    "Y2Fmw6k="   8 Base64 chars
a waving-hand emoji         2 characters   4 bytes    "8J+Riw=="   8 Base64 chars

Output length is 4 x ceil(bytes / 3), so Base64 always costs about a third more than the raw data. Only bytes are encoded, never characters - which is exactly why emoji and non-Latin scripts survive the round trip.

The two options

URL-safe alphabet swaps + for - and / for _ and drops the trailing =. The emoji above becomes 8J-Riw, which survives a query string, a filename or a JWT segment untouched.
Wrap at 76 characters inserts line breaks for MIME, the width email bodies have used since RFC 2045. Copy takes the wrapped text as shown; the character count ignores the newlines.

This encoder handles text only, not file uploads. Everything runs in the page through TextEncoder and btoa, so nothing you type is sent anywhere.

Frequently asked questions

How much larger does Base64 make the data?

Roughly 33% before padding. Three bytes always become four characters, so 300 bytes give 400 characters and 301 bytes give 404 - a jump to the next four-character block, two of which are padding.

When should I use URL-safe Base64?

Any time the value goes in a URL, a filename or a cookie. Standard Base64's + becomes a space when a query string is parsed and / reads as a path separator. JWTs use the URL-safe form with the padding removed, which is what this checkbox produces.

Does Base64 keep the text secret?

No. There is no key and no secret - decoding needs nothing but the string. Use it to move bytes safely through text-only channels, never to hide credentials.